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Thursday, May 24, 2012

New Inexpensive and More Environmentally Friendly Solar Cell

Researchers from Northwestern University have devised a new design of a solar cell that minimizes the flaws in conventional solar cells — relatively high production costs, low operating efficiency and durability, and reliance upon toxic and scarce materials.

Dye-sensitized solar cells have already addressed some of these issues, but up until now have been very inefficient. Northwestern nanotechnology expert Robert P.H. Chang, however, challenged chemist Mercouri Kanatzidis to design a solar cell that did not suffer from the same problem as the innovative dye-sensitized Grätzel cell, a low-cost and environmentally friendly solar cell that “leaks” (the main cause of the lost efficiency). Kanatzidis’ solution was to design a new material for the electrolyte that actually starts as a liquid but ends up as a solar mass.

“The Grätzel cell is like having the concept for the light bulb but not having the tungsten wire or carbon material,” said Kanatzidis, of the need to replace the troublesome liquid. “We created a robust novel material that makes the Grätzel cell concept work better. Our material is solid, not liquid, so it should not leak or corrode.”

Kanatzidis reportedly “knew that scientists at IBM and elsewhere had been developing good solid electrical semiconductors for years” and teamed up with Chang to try one of them, “a fluorine-spiked mixture of cesium, tin, and iodine,” in solar cells.

Chang, a professor of materials science and engineering at the McCormick School of Engineering and Applied Science, and Kanatzidis, the Charles E. and Emma H. Morrison Professor of Chemistry in the Weinberg College of Arts and Sciences, are the two senior authors of a new paper outlining the development of the new solar cell. The paper was published in the most recent edition of the journal Nature.

The solar cell developed by Northwestern exhibits the highest conversion efficiency so far reported for a solid-state solar sell equipped with a dye sensitizer, approximately 10.2 percent (10% is often considered a benchmark for commercial success). This figure is close to the highest reported performance of a Grätzel cell of around 11 to 12 percent, and is much higher than the 6% previously attained by dye-sensitized solar cells.

“Our inexpensive solar cell uses nanotechnology to the hilt,” Chang said. “We have millions and millions of nanoparticles, which gives us a huge effective surface area, and we coat all the particles with light-absorbing dye.”